1. Field of the Invention
This invention relates to an image printing method and device for printing a bar code image representative of a bar code.
2. Prior Art
A so-called bar code is a technique for describing characters (alphabet, numerals, symbols, etc.) by a combination of parallel (vertical) lines (hereinafter referred to as "bars") of different thickness (width) or arranged at different intervals. Each bar code (symbol) represents binary information which can be optically read by optical reading means, such as an optical scanner provided in a bar code reader and the like. Some bar code readers integrate the function of error detection, and are capable of reading bar codes from any direction. These bar codes are printed on labels and the like, which are attached to books, food products, and like articles, or directly printed on surfaces of articles (or surfaces of wrapper for articles), thereby permitting them to be input by input means (reading means) which quickly inputs binary information, at libraries, hospitals, groceries, etc.
The two values (0 and 1) of the binary information are distinguished from each other by difference in reflectance of darker and lighter portions of the bar code. The darker portions having a lower reflectance (referred to as "black bars") are recognized (read) as one (e.g. 1) of the binary value, while the lighter portions having a higher reflectance (referred to as "white barsw") are recognized (read) as the other (e.g. 0) of the same. The conditions concerning reflectance of light required for permitting bar codes to be read (recognized) are standardized as a standard of the bar code print quality (hereinafter referred to as "the bar code print quality standard", see FIG. 12).
The bar code is a kind of image, and hence images of bar codes (bar code images) can be formed and printed by using a printing apparatus, such as a printer which can print images. In the case of printing apparatuses capable of printing color images, it is possible to print colorful bar code images by setting different colors to each bar having a lower reflectance and each bar having a higher reflectance, respectively. To do this, it is possible, in principle, for store managers to devise various bar codes having desired colors suitable for articles sold at his store, and print them as bar code images on articles, or on labels which are attached to articles.
However, ordinary users have no idea of the bar code print quality standard, and therefore, if they form and print bar code images having desired colors, the images can fail to conform to the bar code print quality standard, which prevents the bar code readers and the like from reading or recognizing them as bar codes. Even if a user knows about the standard or details thereof, it is a troublesome and time-consuming work to set colors of a bar code while paying attention to the standard.